Department of Agriculture
Forest Service, Idaho Falls, Idaho
(Updated June 2008)
Poisonous Plants of
The United States Department of Agriculture (USDA) prohibits
discrimination in its programs on the basis of race, color, national origin, sex,
religion, age, disability, political beliefs, and marital or familial status. (Not
By: Wayne R. Owen, Boise National Forest
all prohibited bases apply to all programs.) Persons with disabilities who
Alexis Collins, Environmental Education Coordinator
require alternative means of communication of program information (Braille,
large print, audiotape, etc.) should contact the USDA Office of
Revised for Southeast Idaho by:
Communications at (202) 720-2791. To file a complaint, write the Secretary
Rose Lehman, Forest Botanist
of Agriculture, U.S. Department of Agriculture, Washington, DC 20250, or
Jared Mattson, Student, Idaho State University
call (202)720-7327 (voice) or (202)720-1127(TDD). USDA is an equal
Heather Trussell, Visitor Information Assistant
employment opportunity employer.
Table of Contents
Horsetails (Equisetum spp.)……………………..4 ___________________________________________________
Brakenfern (Pteridium aquilinum)………………4
Flowering Plants ___________________________________________________
Monkshood (Aconitum columbiana)…………….5
Baneberry (Actea rubra)…………………………5 ___________________________________________________
Dogbane (Apocynum androsaemifolium)………..6
Milkweed (Asclepias speciosa)………………….6 ___________________________________________________
Locoweed or Milkvetch (Astragalus spp.)………7
Water hemlock (Cicuta douglasii)………………7
Poison hemlock (Conium maculatum)…………..8 ___________________________________________________
Hound’s tongue (Cynoglossum officinale)………8
Larkspur (Delphinium spp.)……………………..9 ___________________________________________________
Steer’s head (Dicentra uniflora)………………...9
Spurge (Euphorbia spp.)……………………….10 ___________________________________________________
St.Johnswort (Hypericum perforatum)…………10
Lupine (Lupinus spp.)…………………………..11
Chokecherry (Prunus virginiana)…………...….11 ___________________________________________________
Buttercup (Ranunculus spp.)……………………12
Poison ivy (Toxicodendron rydbergii)……….…12 ___________________________________________________
Elderberry (Sambucus spp.)………………...…..13
Tansy ragwort (Senecio jacobaea)…………...…13 ___________________________________________________
Climbing nightshade (Solanum dulcamara)…….14
Tansy (Tanacetum vulgare)……………………..14
Stinging nettle (Urtica dioica)…………………..15 ___________________________________________________
Corn lily (Veratrum spp.)…………………….....15
Cocklebur (Xanthium strumarium)…...…………16 ___________________________________________________
Death camas (Zigadenus spp.)…………………..16
Poisonous Plants of
Every year, many adults and children become seriously ill by
___________________________________________________ consuming poisonous plants. Sometimes this poisoning is accidental,
and sometimes poisoning is the result of the misidentification or
___________________________________________________ misuse of medicinal herbs. Our beloved animal companions (dogs,
horses, llamas, etc.) may also fall victim to poisonous plants.
___________________________________________________ As a public service, the Caribou-Targhee National Forest has
prepared this brief field guide to the poisonous plants commonly
___________________________________________________ found in Southeast Idaho. We hope this information enhances your
recreation experience. Most of the flowers and plants in the forest are
___________________________________________________ harmless, so please don’t think the woods are full of danger. Take
the time to be informed and enjoy nature in a safe and informed way.
___________________________________________________ Although many of these plants are poisonous, many are attractive
native wildflowers and are used by knowledgeable people for
___________________________________________________ medicinal purposes.
___________________________________________________ For more information on poisonous plants, contact your public
library, your local National Forest botanist, or one of these internet
If you are poisoned; call the Poison Control Center at:
Horsetail (Equisetum spp.)
Horsetails are common in moist, coarse-textured soils. ___________________________________________________
The most common species in forested areas has “leafy” stems, but lowland
varieties are typically leafless. Although the rough texture is enough ___________________________________________________
to keep most people from eating them, young children and horses can eat
enough to cause a stomach ache. Native Americans and early settlers used ___________________________________________________
these to scrub cooking utensils. ___________________________________________________
Brakenfern (Pteridium aquilinum) ___________________________________________________
This large fern can be found in forested areas and in dry upland openings ___________________________________________________
around Idaho. The fronds and fiddlenecks (emerging fronds) are poisonous
unless thoroughly cooked. The fronds can be toxic to horses or llamas if ___________________________________________________
consumed in quantity over a period of a week or more.
Cocklebur (Xanthium strumarium) Flowering Plants
Cocklebur is a coarse weedy annual herb introduced to America from
Monkshood (Aconitum columbiana)
Europe. It is most often found along river banks and lake shores.
The distinctive flowers of the moisture loving monkshood are typically blue,
No human poisonings from cocklebur are known but seeds and seedlings
but a white flowered form is fairly common. The foliage of monkshood is
are toxic and potentially fatal to animals. People with sensitive skin may
similar to the closely related western larkspur. All parts of the monkshood plant
develop a rash from handling the plant. Cocklebur is sometimes confused
are extremely toxic if eaten. Poisoning symptoms include general weakness,
with burdock (Arctium spp.) which is a larger plant having more spherical
and eventual respiratory paralysis. Abdominal pain and nausea may also occur.
burs. Burdock may also cause dermatitis in sensitive individuals but it is not
A fatal dose for an average dog is 0.2 ounces (5 grams) and horses are killed by
poisonous. Burdock root can be eaten as a raw vegetable.
doses as small as twelve ounces (350 grams).
Death Camas (Zigadenus spp.) Baneberry (Actea rubra)
The grass-like leaves of death camas can be confused with wild onions Baneberry is found in wetlands and commonly grows to three feet tall. All
(though death camas lacks the distinctive onion odor) and blue camas parts of this plant are poisonous if eaten, but the roots and berries are especially
(death camas flowers are creamy white). This plant is common in grasslands toxic. While death from baneberry poisoning is rare, symptoms can be extremely
and shrub lands throughout our area. The entire plant is highly toxic and fatal to uncomfortable and include vomiting, delirium, and stomach cramps lasting up to
both humans and animals. Poisoning symptoms include profuse salivation, burning three hours. Symptoms may be worse for children than adults. The berries of the
lips, mouth numbness, thirst, stomach pain, vomiting, diarrhea, confusion, slow baneberry plant are bright and colorful and are especially attractive to children.
irregular heartbeat, low blood pressure and low temperature, difficulty breathing, Baneberry was used as a medicinal plant by American Indians.
coma and death.
Dogbane (Apocynum androsaemifolium) Stinging Nettle (Urtica dioica)
Dogbane is a low-growing plant common in a wide range of dry habitats. Stinging nettle is common in wet areas throughout the forests of southeast
It has milky sap and pink, waxy flowers. The toxic compound is a cardiac Idaho. This thin, upright nettle usually occurs in dense patches. Stinging nettle
glycoside, a chemical that can cause heart failure. Dogbane is especially toxic causes extreme discomfort when touched. Tiny hairs on the stem and leaves
to dogs. The bitter taste of this plant makes accidental poisoning unlikely. This break off readily and leave small amounts of a very irritating chemical in your
plant is sometimes used in herbal remedies and its misuse can cause poisoning. skin. People differ greatly in their sensitivity to stinging nettle and different
A similar species called Indian hemp (Apocynum cannabrium) is tall, upright, areas of your body may be more sensitive to it. Young stinging nettle leaves
and commonly found near low elevation wetlands. It too contains the cardiac can be eaten if cooked properly. Never eat nettle flowers.
glycoside found in dogbane. Indian hemp was used as a fiber source for rope
and twine by American Indians.
Corn Lilly (Veratrum spp.)
Milkweed (Asclepias speciosa) Corn lily is common in forested areas where the soil is consistently moist. It is a
Milkweed is typically found in dry habitats, especially in dry, disturbed areas tall, erect plant, all parts of which are highly toxic and potentially fatal. The
like roadsides, pastures, and dry streambeds. Although eating milkweed is rarely highest concentrations of toxins are in the roots. Early spring foliage seems to be
fatal to humans (because it tastes nasty), livestock occasionally die from eating it. more poisonous than mature leaves. Poisoning symptoms include burning
Young shoots of milkweed can be eaten, but only after thorough cooking. Never sensations in the mouth, vomiting, diarrhea, sweating, blurred vision,
eat parts of mature plants. Milkweed sap can cause a rash on people with sensitive hallucinations, and general paralysis. It may cause birth defects if consumed by
skin. However, milkweed is the only thing the larvae of monarch butterflies eat. pregnant females. The occasional cases of human poisoning have been attributed
So, even though it is poisonous to humans & livestock it is a very important plant to misuse of medicinal preparations. Veratum species are currently being studied
to the monarch butterfly. to treat some types of cancer. This plant was used medicinally by Native
Americans for external afflictions and used in cleansing rites as a purgative.
Climbing Nightshade (Solanum dulcamara) Locoweed or Milkvetch (Astragalus spp.)
The deadly nightshade is a common, slender vine often found in low elevation The genus Astragalus is the most diverse group of flowering plants in the
streambeds and other shaded, wet places. The entire plant, especially its unripe world. Many species of Astragalus are valuable forage for livestock
fruit, is toxic and potentially fatal. Nightshade most often poisons children who (milkvetches), but a few varieties (the locoweeds) are poisonous. Locoweeds
have been tempted to eat the bright-red, ripe berries. Although the unripe, green pose little danger to humans as the toxic effects generally requires consuming
fruit is more toxic than the ripe fruit, children have died from consuming both large quantities of plant material (the seeds and pods are more toxic).
(so don’t take any chances). The toxicity of nightshade varies with the growing Locoweeds can be addictive to horses. Animals “hooked” on locoweed will
Conditions of plant. Symptoms of poisoning include abdominal pain, thirst, commonly display noticeable changes in behavior, may shun all other foods,
restlessness, flushing, and skin irritation. In severs cases, victims may experience and may eventually die.
vomiting, difficulty breathing, dilated pupils, diarrhea, bloody urine, loss of
sensation, and even death.
Tansy (Tanacetum vulgare) Water Hemlock (Cicuta douglasii)
Tansy (not to be confused with tansy ragwort) is a widespread, tall, strong scented Common in damp ground and shallow water, the water hemlock can be
herb, with deeply toothed leaves. It is common in disturbed areas at low elevations. identified by the veins in the leaves that terminate at the bottom of the
The entire plant is toxic and capable of causing severe illness and sometimes death. serrations instead of the end of the serrations as in most plants. This is the most
Tansy is sometimes misused as an herbal tea. Poisoning symptoms include rapid poisonous plant in North America; unfortunately, it is sometimes mistaken for
and feeble pulse, stomach lining inflammation, spasms and convulsions. The dried look-alike edibles. The entire plant is fatally poisonous if ingested but the root
leaves and flowers have been used to kill intestinal worms, promote menstruation, is most toxic (a piece of root the width of a finger can kill an adult human).
and cause abortion. When cut, the root exudes a yellow juice that contains the toxin. Symptoms
occur within 15 minutes to one hour after ingestion and include nausea,
excessive salivation and frothing at the mouth, vomiting, violent convulsions,
and usually death.
Poison hemlock (Conium maculatum) Elderberry (Sambucus spp.)
Introduced from Europe, poison hemlock is easily identified by its purple spotted Elderberries can be found throughout southeastern Idaho. The leaves,
stems. The plant emits a mousy smell when bruised or crushed. Poison hemlock stems, bark, and roots contain compounds that are strongly purgative and
grows in disturbed soils and is often weedy. The entire plant is highly toxic, cyanide producing. Eating uncooked berries may cause nausea, vomiting, and
especially for children. It is more toxic in warm, sunny weather, and young foliage diarrhea. Children can get sick from using hollow elder stems for pea-shooters
is more toxic than mature foliage. Symptoms of poisoning include an initial or whistles. Elderberry flowers and fruits are edible when cooked and are
stimulation of the nervous system followed by severe depression of nervous commonly used to make wine and jelly. Elderberry stems and roots were used
system responses, slowing of the heart, paralysis, and eventually respiratory medicinally as an emetic by Native Americans.
paralysis. Small quantities of poison hemlock ingested by pregnant females may
cause birth defects. This is the plant used to silence the philosopher Socrates in
Hound’s Tongue (Cynoglossum officinale) Tansy Ragwort (Senecio jacobaea)
Hound’s Tongue is an attractive plant with dull reddish or purple flowers. It is All parts of this yellow-flowered, wasteland weed are toxic, potentially
common in pine and Douglas-fir forests. Eating any part of the hound’s tongue carcinogenic, and may cause severe liver damage. This plant is seldom
immediately fatal to humans. Milk from cows that have eaten tansy ragwort
can cause permanent and irreversible liver damage.
and honey from bees that pollinate its flowers can cause the same ill effects as
consuming the plant directly. Livestock that eat tansy ragwort over extended
periods may die.
Buttercups (Ranunculus spp.) Larkspur (Delphinium spp.)
There are many species of buttercups in our area. They typically have shiny There are many species of larkspur in our area. The most common ones are blue,
yellow flowers and are most often found in areas with wet or damp soils. but white flowered forms are not uncommon. A tall species (western larkspur) is
Fresh plants often contain irritant oils which can cause blistering of the mouth found along streams in forested areas. A short species, (Nuttall’s larkspur) is
and digestive tract though this is almost never fatal. Some buttercup species are found in dry soils in both forests and shrub lands. Symptoms of poisoning
more toxic than others and some species are used as medicinal herbs. Buttercups include general weakness and eventually respiratory paralysis. Abdominal pain
are considered more toxic to grazing animals than humans. and nausea are also commonly experienced. Young plants and seeds contain the
highest amounts of toxins and poisonings are more common in animals than
Western Poison Ivy (Toxicodendron rydbergii) Steer’s Head (Dicentra uniflora)
Poison ivy, our most familiar poisonous plant, occurs in many low and mid- Related to the gardener’s bleeding hearts, steer’s head grows in rich, well-
elevation habitats. Its growth form can vary from a low shrub to a traveling vine. drained, organic soils throughout the northwest. Death in humans is rare but
The entire plant (stems, flowers, pollen, and even the smoke of burning plants) is symptoms may include vomiting, diarrhea, severe trembling, and difficulty
allergenic, causing severe and continuing skin irritation on contact for most people. in breathing. Children are at greater risk then adults.
You can also be poisoned by secondary contact with tools or clothes that have
touched poison ivy. The fluid in poison ivy induced blisters contain the compound
that causes the infamous reaction and can cause further contamination (so don’t pop
Spurge (Euphorbia spp.)
There are many species of spurge. In our area, the noxious leafy spurge (E.esula) Lupines (Lupinus spp.)
is most common. Plants bleed a milky juice when cut or bruised. People have died Lupines are found in a wide range of habitats. All lupines share the
from consuming dried plants, fruits, and seeds. Symptoms of spurge poisoning characteristic leaf shape seen in the accompanying picture. All parts of lupines
include convulsions, burning at the mouth, fluid build-up in lungs, and constriction are toxic, especially spring foliage, flowers, and fruits. Lupine consumption by
of pupils. Even licking your fingers after handling the plants can cause burning pregnant females can cause birth defects. Documented cases show cows and
lips and tongue. The milky sap of spurge may cause a rash or blistering in people goats that eat lupines can pass toxins through their milk. Deformities in puppies
with sensitive skin. and human babies have been linked to lupine contaminated milk consumed by
pregnant females. Death from lupine poisoning is rare among humans but
li k h l i i ii di
St. Johnswort (Hypericum perforatum) Chokecherry (Prunus virginiana)
St. Johnswort is an erect herb with opposite leaves, and bright yellow flowers Chokecherry is found throughout southeast Idaho. Although the fruits of cherries
found in dry areas at low elevations. This has minute oily droplets on the stems (Chokecherry and other types of Prunus species) are enjoyed by thousands of
that can cause a skin rash on people with sensitive skin. Consuming large quantities people every year, there have been a few cases of children being poisoned by
of St. Johnswort may cause convulsions, increased heart-rates and temperature, eating a large number of seeds along with the cherries. Cherry seeds, leaves,
diarrhea, and even blindness in both humans and animals. Animals often survive bark, and shoots contain cyanide producing compounds. These compounds have
St. Johnswort poisoning only to die from secondary complications, such as failure caused livestock deaths. Cyanide poisoning initially causes rapid breathing
to eat. This plant has long been used in herbal remedies, and has been identified followed by slow and difficult breathing, anxiety, confusion, headache, low
as a treatment for depression. blood pressure and rapid heart rate. Convulsions, coma, and death can occur
rapidly. Chokecherries are popular in this area for making jams and syrups.